This invention concerns refractory compositions, particularly such compositions as are suitable for nozzle gunning.
Refractory compositions for gunning through a nozzle wherein water or other tempering liquid is admixed with the dry composition just prior to projecting it onto a furnace wall or other structure are well known in the art. Such compositions must contain a bonding material which will react rapidly with the water and promote rapid build-up, with low rebound, of the refractory material as soon as it hits the surface upon which it is gunned. Also, as with other refractory products, it is desired that gunned refractories have reasonably high density, together with reasonable strengths, particularly at elevated temperatures.
Another desirable characteristic of nozzle gun mixes is that they be usable over a relatively wide water range. Achieving the correct amount of water addition requires skill on the part of the gun nozzle operator, and if the range from "too little" to "too much" is very narrow, it requires constant attention and skill to maintain the correct amount of water under practical gunning conditions. Hence, a gunning composition of relatively wide water range is desirable.
When the composition is to be gunned onto a hot surface, for example in repairing a hot furnace or other vessel, the gunned composition should adhere and stay in place without popping or exploding as it heats up to the furnace temperature.
As mentioned, many such gunning compositions are known in the art. For example, U.S. Pat. No. 3,232,774 discloses a nozzle gunning mix of dead burned magnesite, magnesium sulfate, for example Epsom salts or kieserite, and hydrated lime. Also, U.S. Pat. No. 3,879,208 discloses a refractory composition, which can be gunned, comprising refractory aggregate, fine magnesia, aluminum sulfate, and citric acid.
As will be evident from the following specification, the composition of the present invention uses bonding materials individually disclosed in the prior art, but in a unique combination which leads to improved characteristics, particularly wide water range and resistance to popping when hot gunned, compared with prior art compositions.